I'm planning on buying an Optimus G Pro at the end of this week and need to know if it is possible to enable USB Mass Storage mode (AKA UMS) in any way (setting, hack, mod, custom rom, custom kernel, etc etc).

I need UMS in order to connect my phone to my car via USB and listen to my MP3 files. MTP will not work (even says so in my car's manual).

I've asked on a few LG Optimus Pro G forums, but no one really seems to use UMS.

Oh, I should mention that on my current phone (Galaxy S2 running CyanogenMod), I can enable UMS by going to Settings>Storage and pressing the menu key and selecting "USB Computer Connection" then checking "Mass Storage."

Either this doesn't exist on the LG OGP or no one knows how to find it.Does it exist on the OGP too?

As far as I recall, the LG Optimus G Pro has USB host. Most phones don't have settings anymore to enable it- it's simply always available. Once you plug in a USB host OTG cable and a peripheral it activates. The new LG G2 even pops up a selection of likely apps that are appropriate to the device you plug in.

It is odd that your car would want this feature since MP3 players never have USB host. Certainly iPods don't, nor do Samsung and Sony media players. The car usually acts as the host for the (client) media player.

There may have been a misunderstanding (Maybe it's me?)...My car (2010 GMC Terrain) has a USB port that I can plug devices into (Flash drives, phones, iPods, iPhones, etc) and it allows the car to read MP3 files off of these devices and allows you to control file seeking through the car stereo's controls. No bluetooth support for music either; phone calls via bluetooth only.So in other words, it isn't the phone reading the car, but the car reading the phone.

With my current phone (ATT Galaxy S2) my car will not read it at all if it's in MTP mode. I had to install a custom ROM that supports UMS. UMS makes the car see the external memory card as a flash drive.

Every single custom ROM I can find for the LG Optimus G Pro does not support UMS (stock doesn't either). They also use MTP. It's just that I always use my phone as a phone AND an MP3 player both on the go and in my car. I use it to play music through headphones, but also in my car. I'm not really willing to give up car functionality and cannot afford to buy a separate MP3 player for the car.

Unless USB Host somehow makes the phone compatible with my car stereo, I don't think it is of any use to me... right?

OK, I just tried my current phone in my car with MTP and it works now... It reads the phone as "PFD" (whatever that is EDIT: Oh, wait... PlaysForSure!) and shows a music note icon, which it doesn't do with UMS.

So now I am wondering if this is my custom ROM (CyanogenMod 10.2, which is Jelly Bean 4.3) or if it is MTP itself. If it is MTP, then there is a really good chance that my new phone will also work in my car.

Here's the thing:When I first got my Galaxy S2, it had Gingerbread 2.3.6 on it, which only used UMS.

Then it got updated to Android 4.0.x (it was either .3 or .4), which started using MTP by default, but still had UMS hidden on it. The MTP wouldn't work in my car though, so I had to jump through the hoops in order to enable UMS every single time I connected the USB cable.

I then began using a custom Jelly bean ROM since ATT was taking forever to release their bloated version of Jelly Bean. Because MTP didn't work in ICS, I just never used it again, assuming that it would never work with my car.

Glad you got it working! I think we're confusing two things. For some reason, I thought you were asking about USB host is where the phone acts like a computer and you can plug USB peripherals into it like mice and flash drives. USB Mass Storage mode for syncing means the phone emulates removable storage (flash drive or SD card for example) when connected to your PC (as opposed to connecting via MTP which is the default with Android 4). LG phones do MTP, PTP, tethering and PC Software mode (for using LG desktop software with the phone). You're right that it doesn't have mass storage mode.

Many media players use MTP, and my guess is that your car should support that. Part of the problem with the GS2 might be that Samsung had an odd way of implementing MTP for their first few phones with that profile, and they didn't play well with several things including Mac computers. Alternative ROMs might have provided a better stack.

Thanks for that info I was driving around town today with my GS2 in MTP mode and connected to my car and I discovered that while it works, it only slightly works for some reason. The car is only reading a few songs, which repeat over and over again. In UMS mode, the car reads all my music (or at least the first 2500 songs since this is its limit).

I am REALLY hoping that this is just another case of my stupid phone acting up again and that this won't happen with the LG phone. I mean, hearing the same exact song over and over again makes you want to pull out your hair!!

EDIT: I just returned to the stock firmware (latest ATT Jelly Bean version) and it turns out that what I remembered about MTP is true: It doesn't work. So the only reason why MTP semi-worked was because I was on CyanogenMod. UGH! Now I'm worried about the new phone not working again!

Like I said, whatever Samsung did to MTP in the Galaxy S II era was a mess. That doesn't mean your new phone will have that problem. So far MTP behaves normally on my LG G2, for example. I don't recall having any problems with it on the Optimus G Pro either.

I just got the OGP yesterday and the first thing I tried was to connect it to my car. It works and yet it doesn't.

Even though the phone only does MTP, my car does read the internal SD of the phone. This would be OK if the internal SD's available space was truly 32GB, but because of how the phone is designed, the actual memory available was more like 22GB. If you install a bunch of apps, then that space will decrease even more. Simply put, all my music wouldn't fit anyways. I have about 1GB more than 22GB and I don't want to max out internal storage (I like apps!).

I didn't take the chance to see if this new phone has the same issue as my old phone, where the car only reads a VERY small portion (30 out of 1000+) of the music collection. I'm thinking that when this issue happened with my old phone, it could have been my car... I can't tell for sure and honestly could care less now.

I decided to just use my phone as an MP3 players for my headphones and I bought a separate memory card for my car. It's not what I'd prefer, which is a single device with all of my music on it, and could be played with both headphones and my car... but it works. So problem not solved, but worked around.

Overall, I am absolutely loving this phone though!Thanks for your help Lisa, and for your OGP review! (I watched it like 100x and compared it to your reviews of the other current smartphones!)